Built up metal tube, frame and skeletonized metal member of high strength weight, and method of forming same



OgtQlO, 1933. R. H. ROBINSON 1,930,285 BUILT UP METAL TUBE, FRAME AND SKELETONIZED METAL MEMBER OF HIGH STRENGTH WEIGHT, AND METHOD OF FORMING SAME Filed May '27, 1929 5 Sheets-Sheet l Oct. 10, 1933. R osmsou 1,930,285

BUILT UP METAL TUBE, FRAME AND SKELETONIZED METALMEIIBER OF HIGH STRENGTH WEIGHT, AND METHOD OF FORMING SAME Filed May 27, 1929 5 Sheets-Sheet 2 WWW 1,930,285 BUILTUF METAL 'ruBE, FRAME AND SKELETONIZED METAL MEMBER OF Y Oct. 10, 1933. R. H.ROBINSON 7 HIGH STRENGTH WEIGHT, AND METHOD OF FORMING SAME Filed May 27, 1929 5 Sheets-Sheet 3 so a: Z9 79 2 9/ 74 7219 3:5?

. I I fig $050550 $m m orngys. I

Oct. 10, 1933. R ROBINSON 1,930,285

BUILT UP METAL TUBE, FRAME AND SKELETONIZED METAL MEMBER OF HIGH STRENGTH WEIGHT, AND METHOD OF FORMING SAME Filed May 2'7, 1929 5 Sheets-Sheet 4 HULL 0ct. 10, 1933. R, H, Bl 1,930,285 BUILT UP METAL TUBE, FRAME AND SKELETONIZED METAL MEMBER OF.

HIGH STRENGTH WEIGHT, AND METHOD OF FORMING SAME Filed May 27, 1929 5 Sheets-Sheet 5 Patented Octi 10, 193:3

PATENT OFFICE BUII IT METAL TUBE, FRAIVIE AND SKELETONIZED METAL MEMBER OF HIGH STRENGTH WEIGHT, AND METHOD OF FORMING SAME- Roy H. Robinson, Chicago, Ill. Application May 21, 1929. Serial No. 366,131

15 Claims. (01. 113- 116) This invention relates to metallic tubing and other skeletonized metal frames and assembled metal members, having a general appliEation in manufacturing arts, but particularly concerned with structures where exceptionalstrength with 7 minimum weight are essential, such as aeroplane and dirigibleconstruction, metal rackets for tennis, squash and kindred sports, metal shafts for golf, etc, and while applicable to other metals is particularly concerned with' the use of the modern steel alloys of high tensile strength obtained through heat treating process, and the metallic or molecular uniting of various elements of a built up metal structure in an in expensive manner, while simultaneously bring-- ing out the physical properties of the metal obtainable through heat treating.

Of-particular importance in the scope of this inventionare improvements in the reinforcingof lightwalled sheet and tubing with additional strengthening elements at strategic points or forming skeletonized tubing as disclosed in my co-pending applications, Serial Nos.- 103,773, filed April 22, 1926, and 170,777, filed February 5' 25, 1927, and Patent No. 1,636,867, dated July 26,- 1927, and still further, the economical and successful forming of high strength built-up tubing as a substitute for the much more expensive drawn seamless tubing now employed, and without the weakening efiects of welding or riveting or ordinary brazing.

A further object of my invention is to permit of the increase of rigidity. by so forming skeletonized members of thin metal that the design of the product made: .possible by my method of 1 manufacturing, offsets the low bulk modulus of steel alloys where. the strength-weight unit isso highly developed.

It has been found in practice in connection with steel alloys such as chrome molybdenum, chrome vanadium, etc., that a tensile strength of even four and five times that of mild steel is obtainable by heating same to approximately 1625" to 1675 F. and then quenching in water or oil, the material subsequently being drawn or tempered at a lower temperature to produce the combination of ductility and strength desired.

In heat treatment of metals, it is recognized that it is detrimental to carry them above the critical temperature, or to take. them to the critical'temperature more than once. It is also detrimental to shock the material by heating it locally or suddenly as with a brazing torch or welding. In the case of welding, the metal is furthermore transformed. at and adjacent to the welding point to cast steel resulting "in change ofphysical properties, brittleness, loss of fatigue resistance, and failures.

Because of these difficulties, it has been found 0 necessary, to secure the best results, to draw tubing at great expense, and even then any brazing or welding of joints and connections, thereafter, is a detriment to the strength and life of the structure. also destroys the effect of heating treating and tempering previously done to the steel alloy.

It is also impractical to braze with a torch at high temperatures or electrically 'weld thin gauges of metal, the metal being burned through 7 in addition to other difficulties.

If, as in present practice, it is desired to heat treat a brazed steel product, it is necessary to use a spelter of a substantially higher melting point than the heat treating and quenching-temperature of the steel. Thus, for an alloy of chrome molybdenum or chrome vanadium, which is heat treated and quenched at a temperature between 1625 and -1675 R, the customary bronze or brass spelter melting from 1600 to 1650 F. cannot be employed as it would melt in the subsequent heat treating of the steel. Instead, a high melting spelter,-such as silicon copper, melting between 1800 to 1900 F. is employed. In brazing with this,'the steel is heated farabove its critical stage which is injurious to it and in addition, where flame brazing is employed, it is locally shocked and injured by the necessary high brazing temperature. If preheated, the liability of the shock still remains while the dimculty of holding and brazing, with a torch, particularly small and light elements, such .as wire and thinsheet, while keeping them heated, is extremely difiicultand quite impractical in most cases.

Riveting weakens the structure on account of the riveting'holes and with extremely thin gauge metal, the rivet hole has accordingly diminished strength and holding power. 'It is also often found difilcult to secure suificient room for the number of rivets required and the riveting is found difficult of access and troublesome and expensive.

The purpose of my invention is to avoid all these difficulties and secure unusually light metal structures of exceptional strength and, due to novel skeletonized forms made possible by my forming and assembling process, greatly enhanced rigidity, and at the same time minimize costs of production. This is accomplished by The brazing or welding 5 brazing or otherwise molecularly joining or connecting the various elements with the brazing strength which can be predetermined and carried out or regulated in a way best suited to its purpose or use, either in an integral or one-piece structure in the way of a reinforcement or reinforcements, or in a composite or assembled unit structure with a continuity of strength and bracing effect throughout the entire structure, and other particular advantages in various fields of endeavor, as will hereinafter more fully ap pear, especially in air craft construction.

In the accompanying drawings, Figs. 1 and 1 are sectional perspective views of a doublewalled sheet metal tube built up of spirally formed sheets or strips.

Fig. 2 is a sectional perspective view of a sheet metal tube formed with interior reinforced ribs.

Fig. 3 is a sectional perspective view of a sheet metal tube formed with exteriorly crimped corrugation containing wire reinforcement.

Fig. 4 is a cross section of another form of a double-walled tube with crimped interior ridge reinforcements.

Fig. 5 is a cross section of asingle-walled tube formed with a crimped or lock joint from a plain sheet having exterior wire reinforcement.

Fig. 6 is a cross section of a sheet metal tube having the exterior wire reinforcements sunken in corrugations formed in the sheet.

Fig. 7 is a cross section of a sheet metal tube formed with a lock joint from plain sheet and having exterior wire reinforcements located in corrugations.

Fig. 8 is a cross section of a sheet metal tube formed with interior andexterior walls spaced apart by interior metal reinforcements.

Fig. 9 is a cross section of a tube similar to Figure 8 of somewhat modified form.

Fig. 10 is a cross section of a sheet metal tube having inner and outer spaced apart walls separated by corrugated sheet wall.

Fig. 11 is a cross section of a double-walled tube formed of folded sheet metal sections disposed between reinforcing connectors, ribs or beams.

Fig. 12 is a sectional perspective view of a sheet metal tube formed of sheets folded to form interior longitudinal transverse walls radially, diametrically, or otherwise extended and having additional reinforcement between them.

Fig. 13 is a sectional view of a tube similar to Figure 12 only formed in polysided or square formation with reinforcements at the corners.

Fig. 14 is a sectional perspective view of a sheet metal tube with interiorly brazed corrugated partitions and locked flanges exteriorly.

Fig. 15 is a sectional perspective view of a sheet metal tube' formed of a sheet withlocked exterior flanges. I

Fig. 16 is a sectional perspective view of a stream line tube formed of two pieces of sheet.

Fig. 17 is a sectional view of a tube formed of four pieces of sheet metal with two additional interior pieces forming partitions.

Fig, 18 is an elevation of a truss of tubular construction.

Fig. 19 is a sectional view taken on section line 19-19 of Figure 18.

Fig. 20 is'a cross section view tal-ren on the section line 20-20 of Figure 18.

Figure 32.

Fig. 21 is a sectional view taken on section line 21-21 of Figure 18.

Fig. 22 is an elevation of another form of built-up truss.

Fig. 23 is a sectional view taken on section line 23-23 of Figure 22.

Fig. 24 is a sectional perspective of the reinforcement on the web trussing of Figure 22.

Fig. 25 is an elevation of another form of tubular truss.

Fig. 26 is a sectional view taken on section line 26-26 of Figure 25.

Fig. 27 is a fragmentary longitudinal section of the bottom cord at point of connection with the web strutting at 2727 of Figure 25.

Fig. 28 isa cross section of an airfoil or aeroplane wing.

Fig. 29 is a sectional view taken on line 29--29 of Figure 28.

Fig. 30 is a fragmentary section of an upper outer wing covering shown in Figure 28.

Fig. 31 is a fragmentary sectional view of a modified form of wing covering shown on the bottom of the wing in Figure 28. v

Fig. 32 is a fragmentary sectional perspective view of another type of aeroplane wing.

Figs. 33 and 34 are sectional views showing details of attaching wing skin to wing and cross ribs.

Fig. 35 is a general plan of wing shown in Fig. 36 is a fragmentary elevation of the wing shown in Figure 35 showing'the leading edge and interior construction.

Fig. 3'7 is a fragmentary sectional perspective view of another type of aeroplane wing.

Figs. 38 and 39 are fragmentary sectional perspective views of tubes used to form the wing shown in Figure 37;}

Fig. 40 is a perspective view of an aeroplane fuselage of tubular construction.

Fig. 41 shows a sectional end elevation of another form of aeroplane fuselage looking toward the right in Figure 42.

Fig. 42 shows a side elevation of the fuselage shown in Figure 41.

Fig. 43 is a fragmentary sectional view of a corner reinforcement shown in Figure 41.

Figs. 44 and 45 are modified forms of wall construction for fuselage of the type shown in Figure 41. I

Fig. 46 is a sectional 'detail joining of the fuselage covering and framing member shown in Figure 44.

Fig. 4'7 is a fragmentary sectional view of another type of fuselage, being a modified form of that shown in Figure 41.

Fig. 48 is a fragmentary plan of a tennis or other racket employing the principles of Figure 1.

Fig. 49 is a sectional perspective view of a modified and desirable form of tubular fram- 18.

Fig. 50 is a fragmentary section of a modified form from that shown in Figure 32, of a fabric covering for an aircraft wall (such as a.

wing, fuselage, dirig ible, etc.) with a metal support, and

Fig. 51 is a perspective view of a typical form of joining two or more tubes in a truss or other construction.

Referring to the drawings in detail, Figures 1 to 17 inclusive indicate a variety of skeletonized light weight tubes of some of the designs made possible by this method of construction.

In Figure 1 the interior wall or tube 1 of the tube structure is formed spirally from a flat sheet of. metal. Where a high strength light weight tube is to be constructed, this can be formed of strip sheet steel of any desired length tionally thin wall, as for example, #30 gauge or ered with a fusing element or layer 2 prefer-f 4 ably in the form of a thin rolled foilof bronze having high tensile strength and a melting point slightly below the heat treating point of 'the' steelalloy.

Over the fusinglayeris formed the'exterior wall or tube 3 of the tube structure of sheet metal ofsdesired character wound spirally, preferably in an opposite direction to that of the inner wall 1, or where that is not desired,,

spiraled in relation to the interiorwall 1 so that the spiral joints are lapped and do not come adjacentto each other in the formed wall of the tube. The contacting surfaces of the metal elements to be united by subsequent brazing by fusing of the element 2; are coated with flux, such as borax or any suitable fluxing preparation, prior to assemblage where the form of the structure requires this or in other cases :fluxed subsequent to assemblage if desired. I

Where'high strength is'desir'ed, this exterior wall may be of steel alloy similar to the interior wall, but it is to be particularly noted that this double wall construction permits the use of two different metals inside and out, which often times presents great advantages. walls, however, are to have a higher melting point than that of the interior or interposed fusing wall of foil so that they remain intact while the uniting materialbetween them fuses when the assembled structure is heat treated.

In this construction, it is possible to use, where demand-arises, a copper sheet wall on the inside with a steel wall on the outside or vice versa, or a stainless steel .can be us'ed on the inside .or the outside with a different steel alloy, in the other wall where corrosionconsiderations arise.

Any variety of these combinations maybe made and two copper walls may be used just the same as two steel walls. Similarly, the in terior or interposed fusing wall 2 may be formed in a variety of ways, and in place of thin rolled show the tubing formed in an economical way out'of a spirally bent strip steel, the construction is equally adaptable to drawn tubing or look joint tubing of the types shown in subsequent figures. Thus, the inner tube or wall 1 .may be .a drawn seamless tube l as shown. in Figure 1 instead of spiral tubing 1, rein forced by the spiral sheet wall winding 3- upon the outside with the fusing layer 2 between the two, as already described or the opposite combination of a spiral formed tube inside and a drawn straight tube on the outside may be employed. Similarly, instead of the spiral mem-.

her being strip steel, it can be wire 3' spirally coiled in contact with the other tube wall, the

spacing of the coiling being close together or spaced apart according to what is wanted. 7 The Both formed tubes where made of: strip steel can also 1 be straight sections rather than spirally wound,

the outer shells being lapped with respect. to

the longitudinaljoint or joints so as 'not'to' be open 'at any point. The brazingor fusing ma-' terial is also placed at the joints which are joinedin the heat treating. v

'It is to be further understood thatthe coristruction of the walls of the tube permits-of considerable variation to-suit requirements. For example; the inner spiral tube, if desired, may spiral in opposite direction from the outer spiral ,wall instead ofparallel to it, or instead of the jointing being a spiral joint, the sheets can be, run with straight longitudinal joints in any desired number as long as the joints of the inner and outer walls are lapped so as to stag-,

g'er or not to come together so as to give overlap and strength. Similarly, either one of the tubes may be a drawn tube in place of a tube made from a strip, or either one may be a tube formed with a lock'joint. Furthermore, in place of the outer or inner spiral sheet being a closed joint, it may be used simply as a reinforcement with spaced apart spiraling, or in lieu thereof, wire spiral coil 31 may be used on the inside or outside in place of sheet wrapping. Finally the tube need not be restricted to two wall members, but may have any multiple of same in the fused union.

In addition to the wall construction alreadysile strength reinforcing wires or strips 4 placed longitudinally or otherwise. These-can be placed at the points developing maximum resistance to strain. While they are shown fourin number in this instance, a larger or smaller number can be applied in similar manner. Theseare laid on the outside of the tube, as noted, and

between-them and the tube is a layer of fusing foil 2 similar to that already described,-the contacting faces of the wire, the foil and the tube being coated with flux, as already described. In lieu of the foil noted, brazing dust or filings can be similarlycoated in or on the tube. 011 the exterior or where the width of the jwire is not too great to prevent the entrance of the fusing material through capillarity, the fusing ,or brazing dust can be coated on thetube and wire along the edges of the wires 4'so as to be drawn into the joint in the heating process instead of 'a brazing-foil or ribbon insert or wrap- -ping. In some instances,- particularly where othercontacts are desired with the wire, a thin brazing foil can be wrapped around the wire 4 the wire being first fluxed. This provides a fused union with the tube wall and other contacts which it makes when heat treated'as noted. It is also to be noted that the exterior reinforcing wires 4' can be located merely where a special reinforcement is needed and do not'necessarily run the full length of the tube, as will also be described in connection with Figure 48.

Spaced apart at desiredintervals over these exterior wire reinforcements are shrinkage bands 5, preferably of steel alloy similar to those used for the, tube walls. These can be one piece jointless. rings, or theypan be made with a joint having desired turned flanges 6 drawn up with heat treating temperature.

5 and the tube wall 3, and between the contacting faces of the flanges 6 and between the heads and ends of the bolts '7 and the flanges 6. This fusing insert can be either brass or bronze foil or dust or filings, or where desired, a heavy fusing coating may be plated as by electric plating or otherwise on the steel members such as 4,

5, etc.

After the tube has been spirally fabricated in assembly position with its fusing and fluxing elements embodied in it, the metal surfaces being fluxed, preferably before assemblage, it is then ready for heat treating in accordance with the practice customary in high tensile strength steel alloys developed for heat treatment. The tube preferably suspended in vertical position, where vertical furnaces are available, is slowly raised, in accordance with established practice, to the In the case of chrome molybdenum or chrome vanadium, which I preferably employ where high strength and light weight are of first consideration, the tube is heated from 1650? to 1675 F. and held at that point until the fusing metal is certain of being fully fused and. the steel given the required soak.

' At points of exterior exposure or where the mass of metal is lighter and in consequence is heated quicker, I preferably use a higher fusing element or material which fuses at a higher temperature than at points inwardly concealed, or where the mass of metal being greater, the raising of the fusing point is delayed behind other more exposed or lighter sections. Thus, in this particular form, the interior fusing, metal 2 lying between the walls 1 and 3 could be formed of a brass or bronze alloy containing relatively less copper with a corresponding lower melting point, as for example in the neighborhood of 1600 F. Then on the exterior portions between the wires 4 and the wall 3, and between the rings 5 and the walls 3 and wires 4, and the flanges and bolts 6 and 7., a higher melting bronze or brass fusing metal melting between 1625 and 1650 F. could be used. When the fabricated tube is then carried to 1675 F. in the heat treating, all these fusing metals become properly melted and fill the joints between the parts which are later to unite.

At the proper moment; the tube is then quenched in the quenching bath of preferably oil or sometimes 'water or other suitable liquid "according to the nature of the alloy, and the structure simultaneously brazed and heat treated. It is to be noted that the structure is formed with relation to the quenching procedure and that upon the sudden emersion in the quenching bath, certain parts cool and shrink in advance of other parts, however rapid the action. The shrinkage rings 5 in this instance being exteriorly exposed, with the quenching bath flooding more rapidly around the exterior than the interior and also conducting heat far more rapidly exteriorly than interiorly, are instantaneously shrunken hard and tightly onto the steel tube within their grasp while the latter is still expanded from its higher interior temperature and with themselves and with the tube wall. The

same process is repeated as between the exterior tube wall 3 shrinking tightly onto the interior Wall 2.

As a result of this construction with relative location and design at parts prearranged in conformity with subsequent quenching action, the fabricated article can be drawn tightly and rigidly together with compacted fused joints of high tensile strength, and the structure presents one completely and molecularly joined and relatively continuous or integral metallic structure throughout. Thus while the high expense of a. drawn tube is avoided, the economy of a spirally formed or sectional jointed tube is obtained without the weakness of the latter or the expense and weakened structure of a welded or brazed seamed tube. Likewise, at the same time, a tube of remarkably thin wall, not suitable for customary welding, is obtainable, while by the addition of exterior reinforcements of longitudinal wires and rings, or otherwise, a structural jacket of great strength is formed integral with the tube with high strength metal located at strategic points without loading the weight at other points.

As wire is the strongest form of drawn material, surpassing that of sheet or tubular steel, it is also possible by this construction to secure reinforcements of a strength not obtainable if they were originally formed as a part of the tube wall itself.

It will be seen that in this process there is also avoided the use of high melting brazing material which is necessary where a structure of this kind is first brazed and then subsequently heat treated. To develop the physical properties of the steel alloy, such as chrome molybdenum or chrome vanadium, it must be heat treated somewhere between 1625 to 1675" F., but I do not wish to be limited to the materials specified.

While it would hardly be possible to braze such a thin structure with its inaccessible interior by ordinary processes, any parts that could be brazed would have to be brazed with a spelter containing copper sufficient to raise its melting point substantially above the heat treating point of the steel alloy. If such were not the case, thebrazed joints would be melted or endangered in the subsequent heat treating, and to avoid such a risk and the possibility of variations in the heating furnace. it is a practice to use a spelter melting somewhere between 1800 to 2000 F. This means that the steel alloy is heated and generally locally at the brazing point to a point far above the temperature at which it is to be heat treated and is also heated more than once to or above the critical temperature. By the method here employed, all the difficulties so arising and any possible injury to the steel alloy and also the strains incurred in the steel by local heating in customary flame brazing are avoided, as also the expense of the two independent processes of brazing and heat treating.

In Figure 2, the tube is formed out of a metal sheet 14 bent to the circular form noted with a locking flanged joint at 15. The tube is also crimped inwardly, as indicated at 16, at as many points as may .be desired to give stiffening, in

this case four, and inserted in the grooves of is approximately flush with the outer surface of the tube, but where desired, this may be projected still further outwardly at'desired points to form fins onthe tube for connections as shown at 17.

Shrinkagerings 5 are placed on the' outside of the tube the same as in Figure 1, only in this instance they are shown as continuous rings which are slipped on the tube from one end instead of being jointed. Either form can be used.

Rings 18 are also placed on the inside of the tube contacting with and supporting the projecting ribs 16 within the tube. These are spaced apart preferably opposite the outward rings 5. It is to be particularly noted, in connection with assemblage of the tube, that the fusing'material, such as bronze foil or in any variety of" form, as already mentioned, is located'between the contacting metal surfaces which are to be subsequently united-that is to say, between the rings 5 and the tube wall 14, between the reinforcing strips 4 land the enclosing walls of the crimps 16, between the contacting surfaces of the inner rings and the bottom of the ribs 16, and between the contacting surfaces of the overlooked joint 15 formed in conjunction with 'a rib or fin 16 and the rib reinforcement 4 so that all the adjacent surfaces of metal have the fusing material 2 interposed between them-in. as-,

sembla'ge, All these surfaces are also fiuxed.

This tube istreated as already described with heat treating and quenching so as to fuse it and bring out the physical properties of heat treating in the one' operationof fusing, heat treating, and quenching. The shrinkage rings,

I 5 draw the outer shell and parts closely together in;forcible contact with the reinforcing ribs 16 and strips or wires' 4', and bearing on the v inner rings 18. The skeletonized structure produced is so strong because -'of its peculiar formation that extremely light weightmetal can be employed giving unusual tubular strength 'withexv ceptional lightness of weight;

' In Figure 3, the tubular form noted is formed with a metal sheet wall 14 joined at 15 and having outwardly extended crimped ridges 16 which other desired form interposed-between the sleeve contain within them, preferably at their outer extremity, reinforcing wires 4. Should the strip of sheet metal not run the fulllengthof the tube, the reinforcing wires 4 can extendon. con tinuously or to coverthe'joint so that when the next crimped sheet is. added, the wirespass continuously from one sheet to another with a broken or staggered joint, jwithout-ajthrough joint in the construction, while-'asleeve 19 can be inserted on'the inside, spanning the joint. The shrinkage bands 5 drawn up with flanges 6 by bolts '7 are spaced apart on the outersurface of the tube, drawing same tightly together, and where there is an end joint, as already described,the ring can cover said joint outwardly with the sleeve 19 performing a similar function inwardly, with the fusing-insert 2 of foil or 19. and the outer shell or wall 14. In this in stance,'the ring 5 is expandedwith a raised ridge rib or bead 20 on its surface to give additionalrigidity., This hollow ridge 20 alsoservesas a container for fusingmaterial 2 ,in the form of foil or brazing dust, which is placed or plastered inside, this ridge so as to contact between thebearing surfaces of the rings 5and. those of v5 the crimped ribs 16. Inside f these ribs 16 is placed the fusing material 2 in the form of foil or brazing dust, or other suitable coating, or a brazing wire as indicated at 2 may be enclosed in the crimped ridge or may replace the reinforcing wires 4 where such reinforcement-is not found necessary. Another method is to wind thewire 4 with the brazing foil, as indicated at 2', so as to cover its entire surface before insertion in the'crimp' The, fusing material is,.

- of course, placed-between the flanges 6 and head but it is more economical to havethem formed of sheet steel joined at 15 and21, as noted.

The contacting surfaces in the crimps 16 are filled with fusing foil or other fusing material 2 which is also placed between. or about the contacting edges of the crimps where they bear on the wall 1- so that all these surfaces are fully united inthe heat treating fuse and .quench. The crimped ridges 16 can also have reinforcing wires, such as 4.in Figures 2 and 3, placed within them, in conjunction with'the fusing insert, if the extra strength is desired. 7

In Figure -5, the sheet wall 14, lock jointed at 15, has wires 4 spaced apart and metallically united to same by placing the fusing. foil at or adjacent to, the contacting surfaces between. the wire and the" tube, so that in the heat treating process they are molecularly united. The fuse 2 is also inserted about the bearing surfaces of the lock joint 15-for thesame purpose. The wires 4 are held to the tube 14 in fusing by permanent shrinkage; rings 5 or otherwise by temporary wiring, serving the same purpose, but subsequently removed;

In Figure 6, the construction is thes ame as ,in Figure 5, only the wall 14 is suitably cor-' rugated to permit the wires 4 to be sunken as noted and the troughs of the corrugation carry the metal fuseinsert 2' between the wire and the tube wall. The tubemay be drawn seamlessor lock jointed, as already shown.

. In Figure '1, the tube wall 14 formed or a sheetwith lock joint 15-has sunken corrugations tend outwardly above the outer surface of wall outer bands-5, the fusing insert 2 being between all the opposing surfaces of the tube walls and seamless or lock' jointed and having inserted between them, as noted, reinforcing wires 4 whichlare'formed with grooves 22 in which is placed-a fusing insert, either in the form of a wire, foil, brass dust .or other coating. After assemblage, the double-walled tube soformed is'heat .treated' and quenched, the outer shell coolingflrst anddrawing hard into the inner Ireinforcementand inner tube with the molten fusing material 2 being forced in the shrinkage and I drawn by capillarity so as to solidify throughoutcthe bearing points with the two tubes..-'

which receive the reinforcing wires 4 which ex-f 1.30 14 and-are held and shrunken in place by the Figure 9 is a modified form of the tube shown in Figure 8, the outer tube 3 and the inner tube 1 being slightly corrugated and the corrugations spaced apart at opposite points so as to receive the reinforcing metal ribs 4, as noted. The fusing material 2, as already described, is inserted in or about the corrugations and the inserted ribs 4 so that the whole is drawn together and metallically united together-in the heat treating and quenching by the united shrinkage of tube 3 and the capillary action of the fuse 2 in the corrugated joints.

Figure 10 shows another form of double walled tube similar to the type shown in Figures 4, 8 and 9, but in this case, the inner and outer walls 1 and 3 respectively are separated by a corrugated sheet instead of by crimping of the tube shell or insertion of reinforcing wire or ribs. The intermediate corrugated sheet 23 is provided with corrugated grooves 24, as noted, for the purpose of containing the fuse insert 2 which, in this case, can be preferably a fusing wire, or the brazing, dust, foil, or other suitable insert or coating. The shells 1 and 3 and the corrugated wall 23 can be either seamless drawn, or can be formed from a sheet or strip with a lock joint, as already noted inthe other tubes. The treatment is the same as already described, the fuse taking place in the heat treating process and the quench drawing the outer tube 3 tightly onto the inner members, the outer shell obviously cooling faster than the inner ones, resulting in a tight brazed connection at all' contacting points between the three wall members.

,It is to be particularly noted in connection with all these wall constructions of this type, whether used in tubular or straight sheet or any other desirable form, that the particular purpose is to skeletonize the structure while cutting down the gauge of the metal so as to give depth to the thickness of the wall formed and consequently increased rigidity, the whole, however, still remaining one metallically united unit. Thus, in a tube of the type shown in Figure 10, the gauge of the outer shell 3 may be half what might be normally the gauge of the intended tube, if it were a single wall, and the inner wall 1 of the same light gauge as 3, the two inner and outer walls weighing less than the double thick wall of a single tube. Or, if desired, the gauge can be cut down sufficiently to allow for even the additional metal of the corrugated wall 23 and where still greater lightness is desired, the wall 23 can be of foraminous corrugated sheet which is punched with apertures or expanded in the form of the well known trussit" commercial lath, whereby an interior reinforcement of great lightness is secured, while a strong truss formation is still maintained between the inner and outer walls of the tube.

It is also to be borne in mind that while for exceptional strentgh, such as is wanted in aircraft and other applications, it is intended to use a steel alloy, preferably chrome molybdenum, chrome vanadium or stainless steel", for the several members of the structures. Nevertheless, the construction applies equally well where one or more of the walls is of copper and the same applies to the combination of other metals as long as the fusing point of the fuse 2 and the heat treating point fall below the melting points of the structural metal members.-

Figure 11 shows another double walled tube obtainable through this construction, which is made economically out of sheet or with seamless drawn sections, if desired. In this instance, the segments of the two wall sections 25 are formed of sheet or strip metal. They are shown with afolded lock as noted at 26, and are assembled in tubular formation with the rein forcements 4 in the shape of metal Is, or, if desired,.Ts, or other suitable shaped, placed between the abutting points. These reinforcements, however, may be omitted and the tubular sections 25 simply abutted end to end. The shrinkage rings 5 are slipped or clamped onto the outside of the tube and the fusing insert 2 is placed between the abutting ends and the reinforcement 4 so as to freely cover the contacting surfaces and likewise between the folded or locked joints 26 and between the shrinkage rings 5 and its bearing surfaces on the tube wall. The assembled product is heat treated, fused and quenched as already described, resulting in a tightly shrunken metallically united two walled and ribbed reinforced tube, which can then be drawn to desired temper. The construction in all steel alloy will give enormous strength while if a copper tube is desired with steel reinforcement, the section 25 can be formed in copper and the ribs 4 in alloy steel. Other .combinations of desired metals can similarly be arranged in all of the structures, according to the needs of the situation and in conformity with the reouirements already set forth.

Figure 12 shows a tube formed out of sheet or strip metal in such manner as to produce strong interior bracing walls. In this instance are shown four sections 27, each being a quadrant, but any number of segment sections can be used in the same manner, and the form of the finished tube may be circular, elliptical, square, octagonal, or whatever may be desired. Each section 2'7 is shown as folded out of a single sheet with a lapped joint 28, which makes an extra reinforcement between the partition walls 29 at the center of the tube, and, where desired, an extra reinforcement 4 in the form of a metal strip may be enclosed at the outer edge of the tube between the walls 29. This reinforcement also may extend outward as a fin the length of the tube or merely at points where desired to attach connections thereto, or where extra rigidity or reinforcement is wanted. Between the contacting partition walls 29 of sections 27 formed within the tube is placed an insert layer of fusing foil 2 which also lies between the lapped joint 28 so that all' contacting surfaces have fusing insert about them to take care of the metallic joining in the heat treating process. Where desired, additional reinforcement in the form of a strip or sheet may be laid between the partition walls 29. Where it is desired to have extreme lightness coupled with the exceptional strength of this wall tube,

the inner walls 29 are stamped with apertures 30 which may be in any desired form and they may be opposite each other where an opening between the different sections of the tube is wanted, or they may be in staggered relation. i.-'--' The shrinkage bands 5 with adj .istable end clasps 31 are placed on the tube at desired points of reinforcement and these shrinkage jackets, when the tube is heat treated and quenched, pull it tightly together and with the fusing insert 2,

which is. placed between the shrinkage rings and the tubular wall, a tight metallic unit is formed and the clasp is also sealed with the fusing insert 2 which is placed in or about it.

Figure 13 shows a modified form of the struclot) - being shown as a rectangle, while reinforcing Q ture shown in Figure 12, the shape in this case wires 4 can be placed at the corners and the whole pulled together by the shrinkage rings 5 with the customary heat treating fuse and quench. Otherwise, the construction is substantially as shown and described in connection with Figure 12.

Figure 14 shows a strong type of tube with a transverse diametrical partition 32 and the tube walls 33 being formed of sheet metal folded at one edge to form thelock joint 34 making strong projecting fins on opposite sides of the tube. Inside the lock joint, between the contacting surfaces, is'enclosed the fuse insert 2 preferably foil or other suitable coating of fusing metal. For extra rigidity, the portion of the sheet 32 which lies between the tube is preferably ex-- panded, forming the corrugations 3 5. Shrinkage bands 5 clasp thetube at desired intervals.

and pierce the external fins. at 36,.as noted. The

"fin, if desired, for holding it extra tightly in fusing, may have rivets or bolts 3'? at spaced apart intervals. These have fusing washers 38 between the bearing metal and the edge of the-heads or nuts so that in the fusing process these are e melted and the rivet joint made a molecular unit.

fore, may be spaced far apart.

As the fuse joint 34 metallically unites the tube walls throughout their length, the rivets 37 are not depended upon, but are more in the nature of holding elementsduring the fusing and, there- The fusing insert 2, as customary, is placed between the bearing surfaces of the ring '5, the tube 33 and under the clasp 31, and where the ring 5 passes through the lock fins 34. A brazing dust mixture may be coated around these points in place of an insert underneath to be pulled into the joints by capillarity, and, in such case, to further this action and to give more brazing edges; the. ring or clasp 5 may have perforated holes 39 throughout its length into which the brazing brass, or whatever fusing metal is employed, is coated or buttered together with the flux. The tube is united in one metallic unit in the heat treating fuse and quench, the outer, rings, 5 pulling the structure tightly together as described. It is-to be noted that the construction of the tube in Figure 14 -may be made suitablein shape to fit any purpose and in the case of aircraft can be formed with a stream line cross sectionas desired.

' Figure 15 shows a tube 3 formed of a plain sheet or. strip shaped with the abutting edges 40 turned outward and the joint'covered with another'sheet metal strip 41 bent U-shaped to form v a jacket locked by same, producing a tube with a longitudinal reinforcing fin. This fin is heldtogather at spaced apart intervals for fusing as well as reinforcing by occasional rivets or bolts 37, which are placed with copper'fu'sing washers 38,'similar to those described in Figure 14. The

' fusing insert preferably in the form of foil is placed between the contacting surfaces of the several layers-of metal in the outturned edges 40 and the jacket 41 so that the whole is fused and the tube metallically united when given my heat treating fuse statement. I v

Figure 16 shows a tube 3 of a slightly modified form from that shown in Figure 15 and of stream line cross section. In this case, the walls are formed of two metal sheets or strips instead of one, one set of edges 42 meeting and being turned inwardly to form an inner rib on one side of the tube, while the other. two edges 43 meet and are turned outwardly. The fins are held together at ing material 2 of bronze or brass.

spaced apart intervals by rivets or bolts 37 with fusing washers 38. Fusing foil 2 is placed between the projecting edges 42 and 43 in the customary manner. It is understood that wherever the fusing material is used, themetal surfaces, in all cases, are dipped or painted with borax or a suitable fiuxing material. The fusing material can also be similarly treated. The tube 3 is gripped at suitable intervals by the customary shrinkage rings 5,- which are also held by the rivets 37. When it is desired to join the end of the tube to another structural element after the tube has been completed by the metallically joining heat treating and quench process, a suitable heavy shrinkage jacket 5 employed at the end of the tube furnishes a welding surface permitting with shrinkage rings 5 of steel alloy and the fus- 1:3

I Other metal" combinations are also possible as already noted. Figure 1'7 shows another type of partition tube formed from sheet metal strips, the outer tube walls 3 being separate pieces with outturned edges 1 forming flanges 45. The pieces of sheet metal strip are bent to form the partition sections 46,

two of these pieces being held to'gether by rivets 47 at the center while outwardly they are riveted at 48 to the tube flanges 45, making a strongly l brazed tube when fused together with the fusing insert 2 which is placed between the angular bearing surfaces of 46 at the center and the rivets 47 and between the bearing surfaces at the outer edge between 45 ,and 46 and surrounding 1 u the rivets'48, as already described. The rivets 47 and 48 can be spaced far apart as the fuse 2, After the tube is heat treated and quenched,

- metallically unites the members independently of rivets, The fins on the tube formed by the out- 1 turned edges 45 can be used for attaching connections to the tube and;can be-punched with bolting and riveting holes for that purpose as may be desired. T

While the tubular structures already described will more frequently be used in light small structural elements which in turn can be similarly combined to form larger framing members, it is also to be understood that the same type of skeletonized and tubular designs canbesimilarly .3)

formed on a large scale to serve as large structural bodies such as aircraft wings, fuselages,

seaplane hulls, pontoons, etc., and the structure is not limited to any one field, but is particularly suitable where exceptional strength and rigidity 1Z5 andfatigue resistance of metal are sought in structures of abnormally light weight and where economy and simplicity in structure and assemblage are of prime importance It will be" appreciated that this partition form of tubes, 1

such as shown in Figures 12, 13, 14 and 17; is particularly suitable for designs in aircraft landing gear axles where excessive strength and shock resistance are required and where failure of the axle is certain to'wreck or jeopardize the 1' aircraft.

Figures 18, 19, 20 and 21 illustrate a combination of tubular structures of the type already illustrated, producing a light and strong truss suitable for a variety of structural purposes, but 159 particularly desirable for aircraft spars or longerons or fuselage framing, or for dirigible framing. The top and bottom cords 49 are formed of a tube of any desirable type, but in this instance a plain oval section on which are mounted reinforcing wires 4 for strengthening the tubes and the truss at the points having the greatest radii of yration, the reinforcing wires 4 being metallically joined to the tubes 49 in the manner already described and at the time when the several parts of the truss are similarly united into a complete fused and heat treated metallic unit. The tube 50 bent into the truss form indicated forms the web trussing of the frame work and is attached to the top and bottom cords 49 by the shrinkage reinforcing rings 5. These are slipped on the truss frame 50 and the tubes 49 are then shoved through them, the rings fitting sufficiently snugly, so that the assemblage will hold its position, by slightly squeezing or denting the rings to conform to the tubes so embraced or by shimming same. Between the rings 5 and between the tubes 49 and 50 are placed the fusing insert 2 already described.

For high strength the tubing will be preferably chrome molybdenum or chrome vanadium tubing, and the fusing insert of foil or dust or other coating will be of preferably a bronze alloy with a melting point somewhat below that of the steel alloy. In this as well as all structures, the parts which heat up more slowly because of their inaccessibility or greater bulk of metal, a bronze or brass alloy fuse of a still lower melting temperature will be preferably employed, while at the points heating up more quickly because of thinner section or greater exposure, the higher melting bronze or brass, fuse will be preferably used. By this arrangement in the heat treating process,. the fusing will more nearly approach simultaneous melting so as to hold the fuse better in its proper place and not run it off by too long or too high heating at exposed points. As steel alloys, such as chrome molybdenum, have a range of heat treating temperature of about 1625 to 1675 F. and should be allowed to soak in the heat for proper heat treating, the length of time being proportionate to' the thickness of the metal, it will be seen that with the fuse melting above 1625 and below 1650 F., the structure can be heat treated and allowed to soak at 1625 without running off the fuse by too long exposure and can then be taken up to 1675 for only a long enough interval to melt all the fuse and thereupon be immediately quenched without holding it at that temperature a long time to the possible detriment of the fusing material. In practice the heavier and enclosed metal sections will be found to hold back considerably -in this fusing and at these points, the lower melting fuse material may preferably and should be used in all such structures.

In the form of truss shown in Figure 18 a web trussing 50 can be reinforced for further rigidity by wire trussing 51. The'truss wire 51 is strutted away from the tube 50 by a metal strut 52 which slips onto or clamps around the tubing 50 and'has open eyelet ends 53 that the truss wire 51 passes through. The fusing material 2 is inserted between this strut and the tubing 50 and also in the eyelets 53 and between the wire 51. In the eyelet, a piece of brazing wire can be inserted for this purpose or the truss wire can be wrapped with foil or the whole plastered with brazing dust mixed with flux. In the joint at the time of fusing.

vicinity of all fusing material and surfaces which .are to be united thereby, the metal is dipped or brushed or washed with fluxing material to facilitate the fusing union. As an additional reinforcement to tie the reinforcing truss wire 51 longitudinally, a longitudinal reinforcing wire 54 can be run through the eyelets 53. Where it is desired to use vertical stiffeners between the top and bottom cords of the truss, a tubular strut 55 may be employed as shown. The tube 55 is slitand the ends flattened and opened to fold around the tubes 49 as shown in the form of a collar with outturned edges forming flanges 56 which are held together with rivets or bolts 57, the fusing insert 2 being placed between the flanges and between the flattened ends of the tube 55 and the tube 49 and between the rivet or bolt heads 57 and the contacting flange ends 56; in short, between or about all contacting or opposing metal faces to be joined, as is the arrangement in all these structures. These flange ends can also be used for attaching bolted, welded or riveted connections to the truss at this point, if desired, and a connection plate of any size of the type shown at 58 can be embraced with fusing metal 2 between the flanges 56 as indicated'when desired. Where the two reinforcing wires 4 are used side by side as shown, the fusing insert 2 can be placed in the form of foil between them and the bearing surface of the tube 49, but a very easy way to add the fuse with this form of reinforcement is to plaster the fuse 2, in the form of brazing dust mixed with flux, into the groove 2 formed by the two wires 4, the capillarity pulling this into the At the ends of the truss on the top and bottom tubes forming the truss cords are shown different forms of connection collars 59 and 60. The collar 59 serves the double purpose of providing a holding collar similar to ring 5 for joining the tubes 51 and 49 and at the same time offers an end connection for the truss to be joined to other framing. For that purpose collar 59 may be provided with threading or riveting connections, but in this instance, is shown a V-edge 61 to form a recess for a welding fillet for welded connection. The collar shows another form for a male and female connection with provision for a welding fillet 61. The fusing insert 2 is inserted between the collar connections 59 and 60 and the tubes 49, and may be of any of the several forms, or the inner walls of collars 59 and 60 may be grooved as indicated by the dotted line 62 and into these can be driven brazing or fusing wire 2, as noted.

When the truss is all assembled and wedged together in a firm unit and properly fluxed with fusing inserts between all contacting surfaces or plastered adjacent to joints where capillarity will suiliciently draw the molten fuse within, the truss is placed in a heat treating furnace and heat treated as a whole. Where the trusses are of a larger size, it is preferable that the furnace be of vertical design so as to facilitate the handling and the holding of alignment in the heated structure. After the fusing metal is properly melted and the steel alloy given the proper soak, it is lowered into a quenching bath, such as water or oil, etc., according to the alloy used. and the joints, through sudden shrinkage, strongly and integrally united with the molten fuse producing a metallic frame molecularly united throughout, without strain or injury to the steel alloy while developing the highest physical properties of same. Thereafter the truss is drawn to the proper temperature for the tensile strength, ductility and other properties preferred. At the present time, the use of this general type of tubular truss in aircraft is only obtained through electric or gas welding with much un- Certainty and great expense and detriment to the chrome molybdenum or other steel alloy while for that purpose it is necessary to employ. heavier gauges of metal. The skeletonized structure here disclosed, however, because of its reinforcement, strategically located and metallically united throughout and because of the design and process of uniting, permits the use of much lighter cross sections of metal while obtaining maximum of strength. This is amatter of foremost consideration in aircraft requirements.

Figures 22, 23'and' 24 illustrate still another form of light truss formation in which the web member 63 is formed of light sheet steel alloy reinforced on one or both sides by a web stiffener 64, formed out of light sheet metal with an outturned stiffening rib 64 and having longitudinal angle iron stiffeners 65 for flanges, all formed of light sheet steel alloy. The whole is assembled by a few holding rivets 66, the fusing metal insert 2 in the shape of foil or other suitable form being placed between the contacting faces of the metal before assemblage, themetal being fiiixed either before or'after assemblage, but preferably before so'far as the interior faces of the contacting parts is concerned. After the holding rivets 66,v which may just as well be bolts,

are in place to hold the assembled truss rigidly together, it is then heat treated with the fusing of 2 and quenched to bring out the physical properties of the steel alloy and then drawn. Where the truss is long, as already noted, this should be preferably 'donein a vertical furnace and quenching bath. It will be noted that in the quench the stiffening ribs 65, being held at the spaced apart points by the rivets 66, are drawn down tightly between these holding points in chilling so as to form a tightcontact with the web sheet 63,. forcing the fuse into a well set union. The same action occurs with the flanged reinforcement 65 and the web 63.

In Figures 25, 26, and 27 a modified form of 'light truss is shown where the tubing 6'7, forming the top and bottom cords, is strutted apart by tubes of the type 68 or of the type 69, while the shearing and web stresses are taken up by tension wires 70. It will be noted that the cord tube members 67 may be of any cross sectional shape and of drawn seamless, lock joint, or built up tube, but in this instance are rectangular, formed from two pieces of light sheet or strip steel 71 and '72 bent in a U and then assembled together as shown in Figure 26 to form approximately a square tube with a double wall at top and bottom sides. A very convenient type of strut 68 between these is formed from a light sheet metal tube, in this instance, preferably square or rectangular, the ends being turned outward at either end to form flanges '13 and over these flanges are slipped the shrinkage holding collars 5, the truss'wires '70 being passed through these holding rings 5 and being then turned up tight with a tournique or otherwise held at their crcsisng point 7.4. Another type of strut 69 is formed of a square or rectangular tube in which two opposing ends are cut out atthe connection ends leaving the other two sides tacting faces of the tube members 71 and '72 and the shrinkage rings 5 and the strut flanges '73 and all connection points have inserts 2 of fusing foil, or an adjacent coating of brazing or fusing dust applied after fluxing the surface, and in the case of the dust or filings, preferably mixed with flux. In all of these structures where it is desired to facilitate the operation,

the surfaces which areto be brazed may be .coated at and adjacent to the contacting points with a sticking coat, such as shellac or other suitable material. Before this is set, brazing dust or fllings mixed with flux may be spread over this so as to adhere to'same.

After the truss is assembled, it being understood that the collars 5 are wedged or crimped' to hold tightly together the cord 65 and the struts 68 and 69, the trussing wires 70 are drawn tightly in place and the truss is placed in the heat treating furnace, heat treated, fused, and. quenched, as already described, so as to make a complete molecularly united metallic structure of great strength and lightness, the whole struc-- ture preferably being of chrome molybdenum and chrome vanadium, or other steel alloy, the physical properties of which are brought out by this process and without the injury and .difllculties accompanying welded connections.

Figures 28, 29, 30 and 31 show the adaption of this skeletonized and tubular construction to the formation of a relatively light and extreme- 4 1y strong airfoil or wing of an aeroplane formed throughout of high tensile strength sheet steel alloy such as chrome molybdenum or chrome vanadium which form both the frame and skin or wing covering 77. It has hitherto been neces-- sary or customary to use duraluminum 'or other similar light alloy for a wing covering because of the relatively greater thickness of the sheet as compared with steel alloy of equivalent strength, this thickness providing the necessary rigidity in the skin. Duraluminum is also a good resistant tocorrosion, which is an important. consideration in the exterior of an aeroplane wing. By heat treating chrome molybdenum or chrome vanadium or other suitable steel alloy, greater strength weight can be obtained than in the duraluminum if rigidity can only be supplied. In this structure, this rigidity is obtained by using a skeletonized heat treated steel alloy skin 7'7 of tubular structure and of relatively very substantial depth or thickness, while still maintaining light weight. This tubular shell 77;

having an outer and an inner wall 80 and 81 respectively, is formed of very light gauge steel alloy, preferably 27 to 30 gauge, and preferably in strip form running the entire length of the wing so as to avoid cross joints, if possible. In

forming these longitudinal tubular skin sections, v

82 and 83 with an interlocking hinge end 84- for ,the ends of adjacent sections to interlock. Fusing material2 is placed between the contacting surfacesof 82 and 83 and the surfacesof the interlocking wings s4, likewise between the opposing faces of the crimped ribs 78 and between the T ends 79 and the walls 80. In the alternate ,form of skin in Figure 31, the outer walls 80 and 81 are formed in the same way,

but without the interior crimping, the interior' sit, but formed in this instance with suitable bearing surfaces 86 and preferably with a corrugated groove 87 to hold the fusing material 2 in the form of a brass wire, dust or foil for fusing the bearing surfaces of 86 to the skin 80-81. As noted, the diagonal supporting walls of the tru'ssed sheet can be of expanded metal forming apertures 88 for combining strength with lightness or, instead of expanding the sheet, it may be otherwise perforated in these web sections for the same purpose of lightening.

, These longitudinal tubular skin sections 77 when formed with the fusing inserts 2 within them between contacting surfaces, are laid with interlocking edges upon the supporting cross wing structural ribs 89. Because of the unusual relative thickness of the tubular skin and the high strength of the steel alloy forming the skin, it is possible to space these wing ribs relatively far apart so that instead of using a number of cross ribs centered at short intervals as is now the practice, these latter are eliminated and the few ribs 89 are spaced far apart, serving as supports for the tubular skin '77. The skin for the leading edge 77, it will be noted, is

shaped to a curved formation and can be so,

formed'to suit any desired profile. Either the skin type, Figure 30, or the type, Figure 31, can be used throughout the entire skin structure, top, bottom, leading and trailing edge, and the trailing edge can be formed to a pointed edge, if wanted. In assembling the wing, the ribs 89 are set up in their proper spaced apart position. The skin cells 7'7 are placed upon them with edges interlocking and pushed together tightly and thereupon the outer shrinkage tie band 90 extending transversely completely around the outside of the wing with an end joint bolting it together at 91 is placed directly over each wing rib 89. After theseholding and shrinkage bands 90 are so placed, they are drawnup tightly with a bolt 92 and are designed of such dimension that in doing this, the wing skin sections are forced tightly together as well as tight ly on the supporting rib frame 89. Within the rib 90 which is preferably formed of steel alloy strip stamped in a U form with flanged bearing edges, is placed the fusing insert 2 of foil, dust or suitable brazing coating so that the flanges of the rib will be brazed to the bearing surface of the outer skin of the wing shell 80, when the wing is heat treated. Within the rib 99 when wanted can be carried additional steel alloy reinforcements in the form of wire or strip steel 90. This in combination with brazing insert 2 fuses this into a solid unit.

The frame 89 can be formed of tubing and in a variety of ways, but in this instance, as a matter of economy in production, is formed from two sections of steel alloy sheet stamped with turned in edges 93 so that when the sections are placed oppositely together with the turned in edges 93 overlapping, a tubular frame is formed as indicated in Figure 29, the top and bottom cords and the struts 94 of the rib frame 89 so formed being tubular with d uble walls on two opposing sides formed by the overlapping of the turned in edges as indicated at 93 and single walls onthe two other face sides. Between the overlapping edges 93 and the similar walls of the struts 94, an insert of foil, filings 'or coating or brazing material 2 is inserted 'in the manner described. The same is interposed'between the bearing faces of the ribs and the skin shell members 81 for later fusing. At spaced apart intervals, preferably over the struts 94, are placed hollow rivets 95 for holding the two sheets forming the rib frame 89 together and also providing holes through which to pass steel alloy tie wires 96, which lead diagonally from the top hole over one strut to the bottom hole of the adjacent strut of the opposing ribs. When the ribs are set up in place and rigidly held, these wires are woven through the holes and then, where they pass each other in the center of the spaces between adjacent ribs, they can be twisted together or turned up so as to bring them into tension. In the open rivet holes 95 is then inserted fuse 2 in the form of brazing wire nails or other suitable material. The turned heads of the hollow rivets also have a fuse collar 2 under or about them for the purpose of setting them in the fuse heat treating process. As additional anchorage to contacting surfaces of the skin or shell member 81 and the ribs 89, between which occurs fusing foil or coating 2 over all the contacting surfaces, wires 97 are bent around the top and bottom cords of 89 and with'flattened ends inserted into the ribs 78. Where that form of shell is employed, as in Figure 30, and in any event, in both forms of shell shown in Figures 30 and 31, the wires are inserted similarly between the lapping of the end joints 83 and 84 where they are in contact with fuse 2. When the ribs 87 in the form described are set up in spaced apart position and cellular or tubular shell sections forming the skin are tightly anchored lengthwise of the ribs and drawn up tightly in place by the tightening of the outer ribs 90, a complete wing in one union, with all the bearing or contacting surfaces of its several steel alloy metallic parts throughout having fusing material 2 within or around the parts to be united, is ready for the heat treating furnace. It is to be noted that the ends of the wing are left open or have controlling apertures to admit the quenching bath into one end of the several hollow members and the hollow structures of the wing which extend longitudinally thereof, and the other end is open or left with suitable apertures to let the air out of the same longitudinal cells within the wing. The wing in this condition is suspended in a large vertical heat treating furnace and taken to the proper temperature for developing the physical properties of the particular steel alloys employed. In the case of chrome vanadium or chrome molybdenum each, or both of which combined, are preferably employed under present conditions for the entire structure of the metallic union. The heat treating temperature can be taken up to the neighborhood of 1625- to 1650 and held at that point for a sufllcient period to properly heat the various sections of the wing and to properly fuse the fusing inserts and coatings 2 of the various joints throughout the structure. As already noted, the insert 2 in points less accessive to the heat or where the mass of metal is relatively greater, will preferably be of brazing alloy of lower melting point than the fusing material in more ex posed points or in sections of lighter weight where the heat is more rapid. By this means, a relatively even fuse can be kept throughout the structure so as not to run off the fusing metal prematurely in the quick heating portions. At the desired time, the furnace temperature can be raised to 1675 to insure the melting of all the fuse which will vary in a melting point preferably from around 1600 to 1650", according to prearranged selection of brazing alloys. At the 1675 temperature, the wing will then be transferred in vertical position (preferably by lowering directly) into a quenching bath, preferably of oil, but of either oil or water or other suitable quench adapted to the steel alloy. In this quench, it will be seen that the outer shrinkage ribs or rings 90 chill first, drawing the whole structure tightly together and securing a tight metallic union between the rib and the skin. The control of the quench entering the interior cells of the wing is regulated at the end admission holes so as to time the interior shrinkage of different parts as may be desired and found best in practice, it being understood that the purpose is to regulate and time the admission: of the bath into different parts of the structure in relation to the exterior and to other portions of the structure so that shrinkage of different parts is timed to produce tightening of the-structure in portions and direction wanted. Thus in connection with wires 96 the exterior of the shell of the wing is chilled and set before the interior wires are entirely shrunken, the wires being thus drawn tight as desired. The relative action of different parts cannot be always predicted in this regard, but by experimenting, it will be found which portions would receive the prior chill by the advancing and controlling the quench in order to tighten and set the structure in the form desired. By regulating the admission and expulsion holes for the quench in these portions as determined by experimentation, the finished result of the structure and the fused joining can be regulated in this way.

Figures 32, 33. 34, 35 and 36 show still another method of adapting the tubular skeletonized construction to an aeroplane wing in which the closely placed cross ribs customarily met with in the more common wing types are entirely dispensed with as well as the widely spaced apart crossribs shown in the above type already described in connection with Figure 28. By this means, the construction of the wing is simplified and the wing becomes a longitudinal instead of a transversely formed structure. A further purpose of this design is to: provide an extremely rigid though lightly formed metal skin for the wing which becomes a working part of the longitudinal sparmembers 98, being an integral part of their tension and compression members. These spars 98 which form the longitudinal framing of the wings can be of any desired number and spaced apart at desired intervals. They are formed, as here show'n, out of two pieces of steel alloy 99 and 100, preferably of chrome molybdenum or chrome vanadium strip or sheet steel. These are stamped or drawn with outturned crimped flanges 101 and at desired intervals have apertures 102 stamped in them in any desired shape, in this case shown rectangular and preferablyhaving outturned vertical wings 103 for web stiffeners. Between the two walls 99 and 100 and extending throughout the length of the spar is an inner. webbing of diagonal steel alloy woven wire 104. This is preferably rolled after woven so as to flatten the wires at the joints and rigidly key them. The spars are assembled by placing the walls 99 and 100 together with the web wire 104 between and at the same time placing the spanning cross tie plates or sheet members 105 inside the opposing crimped flanges of the wall sheets as shown. These tie plates are preferably perforated, at least within the zone lying inside the flange ribs, so as to give lightness and to offer extra holdings for the fusing material 2, which is placed within the ribs and about the connection plates either in the form of brazing foilbetween the contacting faces, or brazing dust which can be coated on the contacting faces and. left in the stamped holes in 105 where such occur. The web wire 104 can be coated with the brazing dust or the same sprinkled over the wire after it is laid on the sheet 99 prior to superimposing sheet 100, the whole can then be temporarily held together by holding rivets or bolts 106 with the fuse collars. 107. Only a few of these are necessary as the spar depends primarily on the subsequent fusing for holding its several parts together as a unit.

Itwill-be noted that where it is desired to have the spar continuous without-openings between the lohgitudinal chambers formed in the wing by the same, it is unnecessary to stamp out the apertures 102 in the Web of same, or again the apertures, can be staggered in relation to each other so that one in 99' does not come opposite the similar alternating one in the opposite wall 100. When the apertures are formed, it will also be noted that by this simple means the spar is given a' solid web at intervals to give the necessary strutting between the top and bottom cords, while the shearing stresses are taken up throughout the web and across the apertures by the wire web members 104=.

It will be noted that the extending flange ribs 101, aside from giving a cross section of metal for-the top and bottom cords of the spar, afford resting shoulders on which are placed the inner skin members 108. These are made with outward turned flange edges 109 and are formed convexly to make arches between the "spars, as shown. The central portion of the convex arch being crimped, preferably longitudinally as shown at .110, on this crimp portion are placed longitudinal wire reinforcement either in straight longitudinal wires or diagonal woven wires or a combination of same 111. About these wires and in the corrugations 110 are placed the fuse material 2. The 'fuse material 2 is also placed between the bearing surface of 108 and 109 and the spar facings 99 and 100 and their crimp flanges 101.

It will be noted that the edges of 99 and 100 extending beyond the flange members 101 are spacedapart to permit of the turning in of the flange edges 112 of the longitudinal sections of the outer steel alloy wing'skin 113. The

inner and outer skins 108 and 113 respectively are preferably formed in strips the length of the wing, but should they be used in shorter lengths, this canbe done advantageouslybecause of the dual wall construction and the multiple longitudinal parallel sections, the joints of the 'inner and outer sheet walls being broken in such case in relation to each other and the joints of the longitudinal section beingalso broken in relation to those of theadjoining longitudinal section and preferably being disposed so as to come under and being reinforced by the outer embracing tie bands, rings, or ribs 90. All of the sheet joints are lapped with fusing inserts 2, so that they become continuous in the fusing.

Between the inturning flanges 112 of the outer skin and the extending edges of 99 and 100 are placed the fusing metal insert 2 in either foil, dust or other suitable form. After this is done, the joint is drawn closely together by toggle bolts 114 at spaced apart points. It is not necessary to have these close together, as already noted, because of the later fusing of the joints. The skin on the spars and the outer skin 113 of each longitudinal section can be momentarily bent upward, while the toggle bolt 114 is inserted and drawn up. It is thereafter bent down to close up the longitudinal section and held by the introduction of the toggle bolt 114 from the opposite side in a similarly repeated operation in the adjacent section. After this assemblage is completed, the outer tie bands 90, as already described for Figure 28, are placed at spaced apart intervals outside the skin 113 with fusing material 2 within same and between the bearing surfaces on 113. The ends are riveted at 114 with fusing collar 115 into the trailing edge, where the upper and lower skins 113 meet and terminate. The convex crimped arch of the interior skin at the crown, where crimped, 110, is tightly drawn and rigidly united to the outer skin 113 and the rib through the medium of toggle bolts 1 16 which, instead of having a customary nut for adjusting same, have a short strip of steel alloy 117 which threads onto the toggle bolt 116 and is turned up tight so as to lie lengthwise within the rib 90, and has its bearing surfaces and contacts between itself and 90 covered with the fusing metal 2. In addition, if desired, a bolt or rivet 118 with the bracing collar 119 extending through the rib 90 can be used.

The wing so formed 'may have any portion cut away for an aileron, as for example, the outer section indicated by dotted line'at 120. The connections for the aileron are attached to the spar or skin in any desired manner and can be fused on in the same manner as the rest of the wing construction at the time of heat treating the,wing. The wing can be of uniform depth longitudinally or can be tapered to the outer end in the customary cantilever form of construction. In either event, the ends 121 and 122 are left open or with openings until the wing has been fused and heat treated. They can be subsequently closed in any desired manner.

After the wing is all assembled with the fusing material 2 inserted within the various joints so that all contacting surfaces to be united are in contact with or adjacent to fusing material, the wing is heated, fused and quenched and subsequently drawn to desired temperature in accordance with heat treating process already described. This is preferably done in such manner as to preserve the alignment of the wing andsecure fuse joints tightly drawn together in the chilling by controlled quench, as already described, the wing being preferably heated and then lowered into the quench in vertical position. The lower open end 121 descends into the bath while the upper open end 122 permits the air to be forced out longitudinally of the wing cellular sections and the bath to enter the interior sections from below.. The method of quenching will be such as to chill the outer skin 113 and the ribs 90 first, however instantaneous the action upon the whole structure, with the result that it is drawn tightly together and onto the inner skin 108 while the interior is still hotter because of the quenching bath proceeding upward in the interior more slowly and because of the heat being confined within the interior. This causes the outer skin 113 to force the molten brazing material into the surface of the metal by contraction with pressure into the hot inner shell 108. This is solidified and the opposing walls firmly and permanently united before the interior shell 108 takes its final shrinkage.

This process will be regulated throughout the wing to suit experience and desired results by controlling the admission of the quenching bath within the interior of the wing sections either by partly closing the end 121, leaving admission apertures where wanted or by partly closing the aperture in the air exit end 122, or by other suitable means forming a part of or independent of the completed structure. In this way, the cooling in any of the longitudinal chambers either within the skin or between the two sides of the wing can be controlled and the shrinkage at desired points hastened or held back.

It is to be further noted that the outer skin of the wing 113 can be made particularly noncorrosive by using stainless steel alloy sheet for same, as well as for the outer shrinkage rib bands 90. The dual skin made possible by this construction thus permits of the combination of two different materials in the skin, the inner one.can be selected for certain qualities of tensile strength and resistance to fatigue, as for example, the desirable features found in chorme vanadium or chrome molybdenum steel, while the outer shell can supply the desirable noncorrosive feature of stainless steel.

The gauge thickness of the inner and outer skin walls is preferably much thinner, possibly less than one-third that of the customary duraluminum sheet used. It will be noted that whereas most metal wing skins now in use are formed of duraluminum, a chrome molybdenum or chrome vanadium sheet, if heat treated, would have a higher strength weight ratio. Furthermore, for the inner and outer skins 108 and 113, a gauge of metal of less than half the thickness that would originally be required for a single steel alloy skin can be employed and have still greater strength as well as rigidity than the single steel alloy skin because of the skeletonized structure of the dual skin and the relatively greatly increased depth of same. From this, it will be seen that the structure permits of the use of a very light gauge of steel alloy sheet so that the weight of the skin can be kept approximately equal to or even less than. that of duraluminum or a single sheet of steel alloy, while the strength of the skin is not only greatly enhanced, but the proportion of it and its efficiency which is working as an integral part of the structural spar framing is greatly increased in the structure formed.

In all instances throughout the various forms where two elements of the metallic structure have surfaces to be fused together, particularly where two or more sheets are superimposed on one another to form a composite wall for wing covering or skin similar to that shown in Figure 37, the surfaces are preferably roughened or scoriated with grooves or fitted to enhance the molecway, a double wall of much greater strength and less weight is secured while at the same time the skin becomes a working part of the longitudinal spars and serves in most efficient manner as a stress resisting portionof the struc-' tural framing as well as a wing covering, while the entire wing structure, spars and skin, is ultimately one molecularly united metallic unit throughout.

In Figures 37, 38 and 39, a wing somewhat similar to the one just described formed with sheet steel alloy and wire is shown, particular consideration being given to simplicity of construction for mass production and quick and simple assemblage with little or no riveting or bolting. To construct this wing, sheet metal tubes 123 and 124 of the type shown in Figures 38 and 39 are formed from chrome molybdenum, chrome vanadium or other suitable steel alloy, although the construction, so far as the design is concerned, can be applied to duraluminum or any other metal, which is-equally true of the structures already described hereinbefore.

The tubes 123 are made in different sizes and rectangular shaped to suit the particular longitudinal section of the wing which they are intended to occupy, while the circular tubes 124 are made to correspond with 123 sothat they slip tightlyinsideof same. Both 123 and 124 are made of sheet or strip metal with one or more lock joints 125 and 126, determined by the width of the metal. Both tubes can be continuous or have apertures 127:;and 128 stamped in the sheet, done preferablybefore same is shaped. The apertures can be of any size and shape and spacing, but preferably are of the type shown so as to lighten the web by leaving enough metal for strutting and for the shearing stresses while amplifying thecross section of the metal-in the outer cords or flanges of the beams which these tubes form when assembled. The tubes 134 have crimped depressions 129 corresponding to the interiorly projecting lock joints 125 of tubes 123 so that when the tube 124 is forced inside the tube 123, the groove and the lock joint interlock, while between the two is a band of fuse metal 130, which is laid in the groove 129 before the tube is inserted and temporarily held in place by the end being bent over the end edge of 124 as shown. Any of the other forms for providing the fuse metal insert as already noted can also be used in lieu of the brazing band 130. The tube 124 may be skeletonized to any desired degree and accordingly may be not only of sheet metal but, instead, of wire mesh. Where the tube 123 is to form the leading edge of the wing, it hasthat side with suitable rounded contour as noted. Where the trailing edge isto be formed,'the tube 131 corresponding to 123 is formed with one'side sloped to an edge and a reinforcing bar 132 is preferably placed between the opposing walls for the stiffening of the wing edge against lateral thrusts.

After the tubes 124 have been inserted into tubes 123, the tubes 123 are then assembled in proper juxtaposition to form a completed wing section. In placing them side by side, the fusing insert 2, such as a sheet 'of brazing foil is placed between the contacting sides or in lieu thereof,

the sides may be covered with a-coating of brazing dust and flux. Before assemblage of the contacting metal parts in this and the other constructionheretofore described, it is understood that the surfaces are preferably fluxed, although in some instances, the fluxing can be successfully done by dipping or coating after the parts are assembled. The procedure in this connection will be determined by practice and the nature of the structure, but the brazing unit 2 in its various forms is preferably fluxed before insertion or coating, where its nature permits. After the tubes 123 are assembled in place, they can be temporarily clamped tightly together and the holding and shrinkage bands are then placed around them and riveted or bolted tightly together with rivets or bolts 114 at the trailing edge, as already described.

Where, however, it is desired to have a stronger structure and other advantages which will be noted, additional skin members are added by having still a second outer steel alloy sheet 133 and if also wanted, an intermediate layer of wire reinforcing mesh 134. The wire reinforcing mesh which runs the continuous length of the wing without lateral cross joints is preferably made with longitudinal wires 135 interwoven with diagonal wires 136, these being preferably of chrome vanadium or chrome molybdenum or other suitable steel alloy. It is desirable that the woven wire structure should be rolled under pressure in manufacture so as to be flattened and rigidly locked at the crossing points of the wire meshing, thus giving rigid and flat bearing brazing surfaces for attaching themselves to the surfaces of the contacting sheet steel in the fusing process. Before the wire is placed on the inner skin formed by the outer exposed surfaces of tubes 123, the skin surface after being fluxed, is covered with brazing foil 2 or the customary brazing dust 2 which can be sifted over the freshly fluxed and sticky surfaces either before or after the wire mesh. 134 is in place. After this is done, the outer skin 133 which has beenfluxed on its inner surfaces, which are preferably scoriated as previously noted, is laid tightly on top of the wire mesh. The outer skin 133 is formed of sheets or strips which can run either longitudinally or transversely of the wing, but preferably where joints are necessary can run crosswise with the edges lapped in one form or other under the outer tie ribs 90. The edges of the sheets 133, in this connection, can be turned up to form contacting flanges 137 as shown, which may, if desired, be held together by holding bolts or rivets 138 with fusing collars 115. These flange ribs so formed have .fusing material 2 between their contacting surfaces and fit snugly within the raised rib of the tie bands 90 and also have fusing material 2 between those contacting surfaces. Where desired, these flanges can be omitted and the sheets lapped fiat-with fusing material 2 between the lapping surfaces, and the rib 90 can-be formed with the-raised rib center or can simply be a flat strip band preferably placed over the lap joint of the sheets 133. In any form of band, either flat or ribbed, additional brazing facilities may be offered, where desired,

2 between and adjoining the contacting faces of the walls of 123 and 124. These can be either flat or round wires. Similarly, flat or round steel wires 140 can be inserted, as shown. The bearing surfaces of tube 124 can also be covered with flux and fusing dust at points adjacent and contacting with tubes 123. As additional reinforcement in the leading edge of the wing, 21. steel alloy bar 141 can be placed between the innerand outer skin and the wall of the tube 124 can be given another crimped depression or groove 129 to receive same at that point. It is also to be noted that if additional rigidity is desired in the vertical walls of the wing, wire mesh similar to 104 in Figure 32 can be placed between the contacting walls of contiguous tubes 123 with brazing material 2 before these are laced against each other, producing a three-ply web wall similar to those shown in the spars of Figure 32.

Also, as the wing approaches the central or fuselage portion from the end, the cross section of the longitudinally steel reinforcements as 132, 140 and 141 may be proportionately increased, according to the increased stresses to be met, either by adding additional layers of the reinforcement or increasing their dimension in any desired direction, while the thicknesses of the separate sheets forming the skin may be kept uniform the length of the wing and similarly extra layers of the wire mesh 134 may be added within the skin so as to deepen the total skin thickness and increase the cross section of metal as it approaches the point of increasing load toward the center of the wing.

The tubes 123 and 124 may be shaped of the same cross section throughout their respective lengths and to any shape of wing plan. They may also be tapered in thickness to form a wing of diminishing thickness as Figure 36 for the tapering construction, particularly used in cantilever wings.

After the wing is completely assembled with fiuxing and fusing material 2 between or adJacent to all contacting surfaces in sufficient quantity to provide for thorough fusing and integral uniting of all parts, the wing is heat treated with attendant fusing and quenched, as already described in previous constructions. It may be added that in the vertical heat treating of these wings, the heating may be applied internally in the wing as well as externally, either by lowering electric heaters within the inner tubes in vertical position or by locating burners within or at the lower parts to throw the heat directly inside the tubes or inner chambers of the wing. The nature of the fuse 2 as regards its melting point is preferably varied as already described according to its location in thewing structure so that the slowly heating partsaheld back by their location or cross section of metal are given a relatively lower fusing material than the more exposed orlighter parts so that the whole structure is well timed to approach simultaneous melting. Similarly, the flow of the quench about and into the wing is preferably timed so as to provide the desired shrinkage at desired points in relation to the fusing material and the tightening of the structure and the joints throughout.

In Figure 40 is shown the construction of a fuselage frame formed in one complete unit with tubular elements and without the weakening eflects of welding the parts together as now practiced in the art, while also bringing out the main properties of the chrome molybdenum or other steel alloy used for that purpose. The fuselage frame is formed, as noted, by four corner tubes 142 which form the cords of trusses composing the frame work, the web trussing and struts between the cords being formed by the tubing 143 which is bent, as indicated. To assemble the fuselage frame in the form indicated, the shrinkage holding rings or hands 144 and 145 are placed on the tubing 142 and 143 as noted, so as to hold same firmly together. Where continuous rings 144 are used, the corner tube 142 is shipped through same after it is located on two of the truss tubes at each joining. Where the bands 145, which can be either bolted or riveted or clasp bands, as already described in previous tubular forms such as 5 in Figures 1, 3, 16 or 12, 14, etc., are used these are clasped in place after the cord and web trussing tubes are in juxtaposition ready for connection, with comparatively little or no riveting or bolting and no welding. The web tubing 143 can be bent in any desired strutting or truss form, in accordance with conventional engineering practice. At the points where it is held by the shrinkage collars 144, it is slightly flattened so as to conform somewhat to the tube 142 and provide a good bearing against it for future fusingas the fusing insert 2 in the form of brazing foil, wire, dust or coating is interposed between and about the bearing surfaces of these contact- 105 ing tubes and also the inner surfaces of the shrinkage rings. 144 or about their edges.

The ends of the corner tubes 142 at either end of the fuselage can be furnished with any desired connections such as flanged collars 142 for terminating the fuselage or connecting the same with the engine structure at one end and the rear stabilizing, elevating planes, and rudder framing at the other, end, all of which or the connections for which are preferably attached to the frame work of the fuselage, i. e. either the tubes 143 with the brazing insert 2 between the contacting surfaces and 142 or both. Where necessary for tightening up the holding rings 144, steel wedging shims 144 can be forced in between the collars and the tubing in addition to the brazing metal, or the rings 144 can be distorted to conform to the encircled tubing so as to hold same tightly. The similar bands 145 can be drawn up with boltsv to hold same as tightly as desired. The tubes 142 or 143 can be' additionally reinforced with wire or other metal members held within the clasping shrinkage members 144 and 145 after the manner of the construction already described in the truss formations shown in Figures 18 and 25, the construction details of which process are also adaptable to form an entire fuselage similar to Figure 40. It will be understood, as already described, that the entire fuselage framing after being assembled with the fusing inserts in or about albthe interlocking members and bearing faces of the several parts which have also been fluxed, is inserted in the heat treating furnace, preferably a vertical one designed so that the fuselage may be heated in vertical position, and then lowered into a suitable quenching bath, as oil, after the same has been fused and held for the proper length of time at the heat treating temperature. The details as to the fusing temperatures and use and treatment of fuses are the same as already described.

In Figures 41 and 42 is shown a modified type of fuselage where both the enclosing and framing requirements of the fuselage are provided for entirely in metal construction by adapting .the cellular or tubular frames already shown vto this purpose.

The walls of the fuselage in this instance can be formed of panels 146 and 147, preferably curved. The convexity. of the sides provides strong resistance to external strains that the fuselage may be subjected to and the curvature may be such as to approximate a circle. or merely present four opposing curve sides as shown. The panel of the type 146 is formed from sheet or strip alloy steel, preferably chrome molybdenum or chrome vanadlum with turned edges 148 at the edges as shown, two sheets being placed together to form inner and outer walls 149 and 150 respectively, while an inner sheet 151 of the same material formed in corrugated shape is interposed between the two walls to attain great strength and give the wall depth with the minimum amount of weight and metal. The sheet 151, as already noted in similar wall construetion described (see Figures 10 and 28 to 31 inclusive) can also be of the expanded metal trussit form or can be the perforated sheet. The bearing points which eventually become fused to the walls 149 and 150 have slightly corrugated troughs 152 for holding brazing wire 153 or this wire 153 can be reinforcing steel wire, when desired, combined with brazing metal 2 and also placed in the trough or bearing face for joining same to walls 149 and 150. The ends of the panels 146 where formed by the folded edges 148 can be abutted directly'against each other or where additional reinforcements or framing members are desired, a steel alloy T member 154 may be inserted running the length of the fuselage and preferably extending out ward at the forward end when connections to other framing such as the engine framing so require. The reinforcing T 154 is preferably formed of a piece of steel alloy sheet folded as indicated in-Figure 43 and provided with perforations 155 which both lighten it while at the same time forming pockets which can be buttered with a mixture of flux and brazing dust, or receive other brazing insert placed therein. Inside the T between the folded walls, additional fuse insert 2canbe added.

Another type of wall section 147 can be used similarly to 146 either for all four panels or for ,a single panel as for example, the bottom or floor of the fuselage, as shown. This is formed 'with steel alloy sheet or strip metal preferably" of light gauge which is folded and crimped to form a double wall, as shown in Figures30, 31,"

41, etc., and made of sections adapted to the size of the sheet and joined by fusing as at 157',

with bracing Ts between the two walls 156 and 157. Between all contacting faces of the sheet metal is placed the usual brazing insert 2 in any of the forms described, all of these metals being first preferably fluxed. After the wall sections, forming the fuselage, are assembled in position with the reinforcing elements 154, where same are used, the'holding shrinkage bands 158 are placed around same at intervals of desired spacing. These can pass around or, as shown, through holes for same 159 in the T's 154 and the bands 158 can be drawn tightly with a bolt or rivet 160. If it is desired to remove the bands after the fuselage is fused and heat treated, no fusing material is placed between the bands 158 and the outerwall members'150 or 157, but if it is desired to retainsame as additional reinforcement on the fuselage, the brazing insert 2 vided for in the walls.

member 151.

is placed under the band or about its edges and also in and about the holding bolts or rivets 160. Also, if it is. desired to have smooth surfaces on the outside of the fuselage without the reinforcing T 154 projecting, the T can be reversed and the flanges placed on the inside instead of outside of the fuselagaas shown at 154', or a plate corresponding to the-web of the T can be used in place of the T, eliminating the flanges. Where window, cockpit, or apertures are desired in the fuselage, these can be pro- It will be understood, of course, that brazing insert 2 in the form of fusing foil, dust orother form is placed between the bearing surfaces of the panels 146 or 147 and the reinforcement 154 and between all sheet metal bearings throughout together with the fluxing of the metal surfaces and thereafter, the fuselage is heat treated, fused and quenched, preferably in vertical position, as already described.

In Figures 44, 45, 46 and 47 are shownmodifled forms of similar sheet metal fuselage wall construction. Figure 44 provides a single instead of a double wall, the wall being formed of steel alloy sheet 161 with inwardly crimped corrugations 162 and stiffened and held by spaced apart steel alloy channel members 163 which have slots with turned-in edges 164, fusing insort 2 being provided inside the crimps 162 and between or about the bearing surfaces of the slotted turned-in channel walls 163.

Similarly in Figure 45 an outer wall 165 with outward turned crimps 166, all formed out of steel alloy sheet or strip, is reinforced with an inner corrugated sheet similar to 151 in Figure 41, which can "also be of the expanded trussit form or perforated sheet, as desired. These are inner surfaces in the corrugated grooves in combination with fusing material and all the bearing surfaces are prepared with fluxing and brazing inserts or. coatings, as already described, for the panels in Figures 41' and 44.

In Figure 47 is shown still another wall panel combining features of the panel 146 in Figure 41 and that shown in Figure 45, having the double walls 165 and 149 and the interior reinforcing In this instance, a rectangular fuselage is obtained and the corners are preferably filled in by reinforcing quarter-round tubes 170 formed from bent sheet steel alloy, as shown. The outer'wall 165 with the side panel is provided with a long folded edge 171 which gives a bearing surface for the top and bottom wall panels 172. The assembled wall members are held in position by the holding shrinkage bands 160, as already described, these passing through slots 173 in the outward crimp ribs 166. All the contacting bearing surfaces are fiuxed and provided with inserts 2 between them of the fusing material foil, dust, etc., having the proper fusing temperature suited .to its location in the structure, as already outlined, and the whole assembledstructure in a unit is heat treated,

fused and quenched, as described.

- It is to be noted in connection with the above wing and fuselage constructions, that where plane or other conditions will not permit of heat treating an entire length'in one unit, that sec- 

